1. Field of the Invention
The present invention relates to a linear motor provided with a stator and a slider relatively movable with respect to the stator, and more particularly, to a linear motor having a structure capable of easily controlling a gap between the stator and the slider.
2. Related Art
A linear motor has been widely used for a motion guide mechanism or apparatus such as machine tool, industrial robot or the like for moving an object to be moved to a predetermined position with high performance. Such linear motor is generally composed of a stationary member (called hereinlater “stator”) and a movable member (called hereinlater “slider”) in which the slider is supported to the stator to be relatively movable in various arrangement.
A linear motor disclosed in Patent Document 1 (Japanese Patent Application Laid-open Publication No. H09-261943) includes a stator to which a rail is mounted, and a slider is slid along the rail to thereby realize the relative movement of the slider to the stator.
Furthermore, the stator is provided with an armature coil and a drive control circuit for supplying driving current to the armature coil, and the slider is mounted with a field magnet. By supplying the driving current to the armature coil, a magnetic thrust force is generated between the stator and the slider so as to slidably move the slider relatively to the stator.
Moreover, in a conventional linear motor, although the motion of the slider is guided by the rail mounted to the stator, the rail also has a function for retaining a gap in the direction of the magnetic power caused by the supplying of the driving current to the armature coil. In an arrangement in which any gap does not exist between the stator and the slider in the linear motor, the stator and the slider are stuck together by the magnetic force generated by supplying the driving current to the armature coil, which may adversely result in impossibility of the relative motion of the slider to the stator, and accordingly, it is necessary to control or manage the gap between the stator and the slider of the linear motor.
Furthermore, a conventional structure for controlling the gap between the stator and the slider includes, other than the structure controlled by the installation of the rail as mentioned above in the Patent Document 1, in which there is known a linear motor, as shown in FIG. 13, in which a gap G is controlled by the location of a motion guide device 130 including movable member 131 mounted to a slider 121 and a track rail 132 mounted to a stator 110.
Patent Document 2 (Japanese Utility Model Application Laid-open Publication No. S58-186788) further provides a structure for controlling a gap between the stator and the slider, in which either one of the stator or slider is formed with a solid lubrication film so as to form a gap.
However, the structures of the linear motors of the prior art such as mentioned above require guide units or members such as rails extending along the moving direction of the slider, which does not contribute to the reduction of manufacturing cost, thus being disadvantageous.
Furthermore, in the conventional structure, it is necessary to construct the guide unit to the stator so as to continuously extend along the moving direction of the slider, and therefore, it is impossible to adopt a structure in which stators are arranged in plural rows non-continuously with a distance therebetween along the moving direction of the slider, thus also being disadvantageous.
Still furthermore, in the structure in which the solid lubrication film is formed, in order to form the film with a thickness corresponding to necessary gap, it is necessary to grind the solid lubrication film to provide a required thickness after the application of the solid lubrication film. This involves a troublesome working to precisely control the gap.